Is the Caulk in Your Bathroom Really Waterproof?

The quick answer is – yes, when caulking is perfectly applied, but only for the short term does caulk remain waterproof.

Bathtubs and showers are arguably the most hostile environment in your home. Whether you just have dirt everywhere after gardening or your kids are in the midst of potty training, it can be a daily battle to keep your bathroom dry, sanitary and even structurally sound.

Mold and caulking are common conspirators against the sanitary conditions in your bathroom.

It is a myth, if not a falsehood, that caulking is the ultimate tool for what you need to maintain a finished edge, sanitary conditions, or structural integrity of any room in your home.

In the United States, your bathtubs and showers are required by building code to have a waterproof membrane. And, in some areas, a special drywall that is resistant to moisture (usually the green stuff). This water-resistant membrane is supposed to act as barrier behind your bathtub and wall/floor tile. The goal for having the building code is to help make sure the bathroom is set up for the long-term. Note that the loud bath fan above your head is also there to help you eliminate lingering moist air during and after your hot shower.

When it comes to the floors or walls, it is important to understand that the tile and grout used in your bathtub or shower is “porous” and not a impenetrable barrier as it may seem. Different types of tile and grout materials allow differing amounts of moisture through the tile surface. That is why a waterproof membrane is also critical to keeping your floors and walls dry and sanitary. Without this waterproof membrane, it is impossible to stop moisture from migrating through to your walls or under your flooring - which over time will grow mold, will eventually smell and can even become a structural issue if not resolved.

So again, is caulking really waterproof?

Yes, in the beginning, caulking does help keep your walls and floor dry, but you should really view it more as a trim product to finish off the joints between walls and floors. It can work well as a transition between wall tile, where it meets the bathtub deck or where it meets the floor tile. However, even then caulking still becomes a problem when it starts to fail – and can start the domino effect of issues. It is inevitable that moisture and dirt will start to sneak behind your shower, under your toilet, sink and anywhere that mold likes to live.

It’s important to understand that once caulking is applied, you can’t just ignore it until it becomes black with mold, mildew and starts to stink.

Caulking has been around for eons. Are you sure caulking is not waterproof?

Caulking simply will not stay adhered to where you applied it over the long term due to something called hydrophobic surface conditions. Basically, this means that a shiny tile does not let anything stay bonded long term to its surface and over time will cause the caulking to “let go” of the surface on which you apply it. Water and moisture only speed up this product failure.

Every day, DIYers, businesses consumers, and even professionals make assumptions regarding uses for caulk to try to fix a problem. As an example, there are also different types of caulk for different applications – so just buying the cheapest one possible is a recipe for failure.

We created InstaTrim as it will be there for you to work in the long-term in any application. As we have discussed, caulking eventually will let go of the bathtub, toilet, sink or any application you put it.

InstaTrim® peel and stick trim strips are your alternative to traditional caulk that are there for you for the long term. It’s easy to install; simply peel and stick. When you use it with a waterproof membrane, its patented, self-centering wings provide a moisture and mildew resistant barrier for bathtubs and showers for years to come. And, of course, it looks great!